1/f noise is important in mixed signal and analog application because it presents a lower limit of the signal level that can be processed. It is believed that 1/f noise in integrated circuit devices is caused by charge trapping and de-trapping at the traps near the oxide and silicon interface. One conventional process for characterizing the density of interface traps includes connecting a stand-alone waveform generator to the semiconductor substrate and connecting a testing device to the waveform generator. Typically, the testing device is a computer that connects to the waveform generator using an electrical cable that connects to a serial port or a USB port on the waveform generator. However, the waveform generator is expensive and time consuming to set up.
Though conventional in-line testing methods are sufficient for testing the characteristics of semiconductor devices with just a few different types of transistors, processing technologies are moving to processes that use many different transistor types in the same product. For example, a single die can include NMOS and PMOS transistors, low and high threshold voltage transistors, transistors having different thicknesses of gate oxide, buried channel transistors, surface channel transistors, different doping concentrations, different N-well and P-well characteristics, etc.
Accordingly, there is a need for a method and apparatus that will allow for testing semiconductor die that include multiple different types of transistors. In addition, there is a need for a method and apparatus that will meet the above need and that does not require the use of a stand-alone waveform generator.